The present invention relates to a disposable optical cuvette cartridge for spectrophotometric measurements of liquid samples such as whole blood, to methods for constructing the cuvette cartridge and to methods of using the cuvette cartridge.
U.S. Pat. No. 5,430,542 disclosed a cuvette comprising two optically transparent liquid-impermeable sheets, wherein a third adhesive sheet is inserted between the two transparent plastic sheets and the three sheets are pressure sealed together. The adhesive sheet had cut outs defining the contour of an optical chamber, inlet port, and vent port. A liquid sample to be analyzed was placed in the optical chamber through the inlet port in the adhesive layer and the thickness of the adhesive sheet defined the optical path length of the liquid sample within the cuvette.
It has now been found that the disposable optical cuvettes of the art are improved if the inlet port and vent port are present in and pass through one of the liquid-impermeable sheets rather than through the adhesive layer. The invention provides an improved disposable optical cuvette based upon this discovery for use in the spectrophotometric analysis of liquid samples, methods for manufacturing the improved cuvette as well as analytical systems and methods which employ the improved cuvette.
Thus, in a first aspect, this invention provides a cuvette cartridge for optical measurements of analytes in liquid samples. The cartridge comprises a flat, adhesive sheet having a selected thickness that defines an optical path length perpendicular to the plane of the flat sheet. A portion of the adhesive sheet is cut out to define at least one optical sample chamber of a desired length. The sample chamber is completed when the adhesive sheet is placed between and sealed to a first flat sheet and a second flat sheet. The first flat sheet contains a inlet hole and a vent hole which connect to the optical chamber. The vent hole is located at one end of the optical chamber, and the inlet hole is located at a second end of the optical chamber so that liquid can fill the sample chamber. In preferred embodiments, the cuvette cartridge contains a plurality of optical chambers each with its own inlet hole and vent hole.
In another aspect, the invention provides a disposable optical cuvette cartridge for use in the spectrophotometric analysis of liquid samples which employs a pair of parallel sheets of material impermeable to the liquid samples. The two sheets are held in spaced relationship to one another by an intermediate layer which has at least one discontinuity defining a sample zone having a thickness set by the spaced relationship between the two sheets. At least one of these two sheets is optically transparent at the wavelengths of the spectrophotometric analysis and one of the two sheets carries an inlet port and a vent port for each of the sample zones. The thickness of the intermediate layer defines the optical path through the sample zone and the quantity of sample presented for analysis. The thickness of the intermediate layer is also selected taking into account the hydrophilicity of the materials of the various layers to permit capillary action to draw the liquid sample into the sample zone when the sample is placed at the inlet port.
In yet another aspect, the invention provides a method of manufacturing a thin film disposable cuvette cartridge for use in the spectrophotometric analysis of liquid samples. This method involves sealably bonding three flat layers to one another in parallel alignment. The first and third layers are flexible sheets of thin film material impermeable to the liquid samples. The intermediate second layer is also made from a material which is impermeable to the liquid samples. This layer, which has a thickness which is preselected to provide a desired spacing between the first and third films following bonding, has at least one discontinuity. These discontinuities in the intermediate layer define at least one sample zone having a thickness set by the spaced relationship between the two sheets. At least one of the first and third sheets is optically transparent at the wavelengths employed in the spectrophotometric analysis and one of these two sheets carries an inlet port and a vent port for each of the sample zones. The thickness of the intermediate layer defines the optical path through the sample zones and is sized to cause capillary action to draw the liquid sample into the sample zone when the sample is placed at the inlet port.
In yet an additional aspect, the invention provides an integrated system for the spectrophotometric analysis of liquid samples. This system includes a cuvette cartridge into which liquid samples are placed for optical measurements of analytes, an excitation laser, capable of exciting fluorescence in the analytes, and a fluorescence detector capable of detecting the fluorescence excited in the analyte and providing information concerning the presence of the analyte based on the detected fluorescence. The cartridge comprises a flat, adhesive sheet having a selected thickness that defines an optical path length perpendicular to the plane of the flat sheet. A portion of the adhesive sheet is cut out to define at least one optical sample chamber of a desired length. The sample chamber is completed when the adhesive sheet is placed between and sealed to a first flat sheet and a second flat sheet. The first flat sheet contains a inlet hole and a vent hole which connect to the optical chamber. The vent hole is located at one end of the optical chamber, and the inlet hole is located at a second end of the optical chamber so that liquid can fill the sample chamber. The excitation laser is focused on the sample in the optical sample chamber and the fluorescence is detected from the chamber.
The invention also provides an apparatus for firmly holding the disposable thin film optical cuvette cartridge for use in the spectrophotometric analysis of liquid samples in a flattened and registered position as is generally preferred for spectrophotometric analysis of samples contained within the cuvette cartridge. This apparatus is a vacuum chuck which is specifically adapted to work with a cassette cartridge that itself includes a pair of parallel sheets of material impermeable to the liquid samples. The two sheets are held in spaced relationship to one another by an intermediate layer which has at least one discontinuity defining a sample zone having a thickness set by the spaced relationship between the two sheets. At least one of these two sheets is optically transparent at the wavelengths of the spectrophotometric analysis. At least two locating pin holes pass through the two sheets and the intermediate layer.
The vacuum chuck has a continuous perimeter which is shaped to surround the sample zone when a cuvette cartridge is placed upon it and has additional areas within the perimeter. The perimeter and the additional areas are coplanar and define a flat planar surface upon which the cuvette cartridge may be placed. The flat planar surface has indentations extending below the surface defined by the perimeter and the additional areas. These indentations are located beneath the sample zones when the cuvette cartridge is placed on the chuck. The chuck can also present features for accurately registering the cuvette cassette. These can include pins, ridges or other barriers which engage the cassette or markers that may be read by automated registration equipment, or the like. In the embodiment shown in the drawings, the chuck has at least two pins extending upwards from the planar surface and located in the planar surface so as to engage the at least two locating pin holes present in the cuvette cassette. The chuck includes a vacuum source connected to the indentations to apply a vacuum thereto to pull the cuvette cartridge into a locked and registered flat position on the planar surface when the locating pin holes of the cassette are mated with the pins of the chuck.